Display correct filename with --test option
Fixes#39592.
With the current files:
```rust
pub mod foo;
/// This is a Foo;
///
/// ```
/// println!("baaaaaar");
/// ```
pub struct Foo;
/// This is a Bar;
///
/// ```
/// println!("fooooo");
/// ```
pub struct Bar;
```
```rust
// note the whitespaces
/// ```
/// println!("foo");
/// ```
pub fn foo() {}
```
It displays:
```
./build/x86_64-apple-darwin/stage1/bin/rustdoc --test test.rs
running 3 tests
test test.rs - line 13 ... ok
test test.rs - line 5 ... ok
test foo.rs - line 2 ... ok
test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured
```
```
` ``
println!("lol");
` ``
asdjnfasd
asd
```
It displays:
```
./build/x86_64-apple-darwin/stage1/bin/rustdoc --test foo.md
running 1 test
test <input> - line 3 ... ok
test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured
```
r? @alexcrichton
* Don't disambiguate if there are multiple impls for the same type.
* Disambiguate for impls of &Foo and &mut Foo.
* Don't try to disambiguate generic types.
This is the full and proper fix for #32330. This also makes some effort
to give a nice error message (as evidenced by the `ui` test), sending
users over to the tracking issue for a full explanation.
Fix full path being output with `rustdoc -h`
rustdoc would output the full path to the binary when calling it with
the `-h` or `--help` flags. This is undesired behavior. It has been
replaced with a hardcoded string `rustdoc` to fix the issue.
Fixes#39310
Add warning for () to ! switch
With feature(never_type) enabled diverging type variables will default to `!` instead of `()`. This can cause breakages where a trait is resolved on such a type.
This PR emits a future-compatibility warning when it sees this happen.
rustdoc: fix doctests with non-feature crate attrs
Fixes#38129.
The book says that any top-level crate attributes at the beginning of a doctest are moved outside the generated `fn main`, but it was only checking for `#
